Oswald lived as a youth in exile amongst the monks of Iona and was thus baptised a Christian although much of Bernicia, the land of his birth remained ignorant of the faith.
On the eve of the Battle of Heavenfield he saw a vision of Columba who foretold of his victory and in thanks for the recovery of his kingdom "he filled the land with churches and monasteries" as The Venerable Bede recounts. So Oswald is accorded a place of particular honour amongst the kings of Northumbria for his establishment of the Christian faith amongst the Angles of the north.
After his brutal death at the hands of the pagan Penda on the field of Maserfield his body was dismembered and his limbs displayed upon the field of battle. His head was recovered and returned to Lindisfarne and his arm and hand, which remained entire and uncorrupted unto Bede's time, where taken to St. Peter's church in the royal city of Bamburgh and where they were kept in a silver case. The Venerable Bede recounts of the many miracles that where occaisioned both at place where Oswald was killed and by his holy relics including the deliverance of people possessed by the devil and many miraculous cures effected.
In recognition of these attested miracles and his piety he was canonised a saint some fifty years after his death with the day of his death on the 5th August being celebrates as his feast day.